In my copending patent application Ser. No. 211,359 filed Nov. 28, 1980 and entitled FULL FUNCTION IN-PLACE WELD HEAD there is shown and described the weld head structure supporting a horseshoe-shaped carriage mounting a welding torch in such a manner that the horseshoe carriage can rotate about a pipe axis to effect a complete 360.degree. weld.
The torch itself is oriented to extend radially inwardly towards the axis of the pipe so as to be generally normal to a tangent to the pipe at the pipe surface as well as normal to a lateral line parallel to the pipe axis on the pipe surface.
There are certain types of welds, however, referred to as "socket welds" wherein a higher quality weld can be achieved if the torch can be angulated so as to better treat the opposing surfaces to be welded together. Such socket welds are defined between two surfaces which intersect at an angle. For example, where a pipe of one diameter is being welded to the end of a pipe of a larger diameter and there is a face or front surface on the pipe of larger diameter normal to the axis of the pipe, the weld area is defined by surfaces which intersect at essentially right angles and extend annularly over 360.degree.. To effect a weld at this intersection, the torch would best be oriented at 45.degree. rather than extending radially inwardly. In fact, it would be difficult to effect the weld at the proper location if the torch extended inwardly since the side of the torch would interfere with the facing surface of the larger diameter pipe. To effect a weld at the intersection point would by necessity require that the torch head be angulated to "reach into" the weld area.
With presently available equipment such as my heretofore referred to automatic 360.degree. in-place welding system, it would not be possible with the torch oriented as it is in such system to effect suitable socket welds. The same situation obtains for larger welding apparatuses incorporating travelling carriages for carrying a torch head about the circumference of a pipe either externally or internally. As a result, it has been necessary to make most socket welds by hand rather than by automatic equipment.